Logo

2006 Honda 4 stroke 8 HP motors keeps shutting off

Lamiglas

New member
Hi there. I joined the forum hoping someone here might be able to help. This is my father in laws boat and we are struggling to find the answer. The boat has a 115 HP Honda mai motor and an 8 HP Honda for trolling. One gas line comes from the tank, then it splits with one line going to each motor. The big motor runs great with no issues. The 8HP starts great, but dies after 5 to 15 minutes of use. As soon as it dies, it starts up immediately as soon as the start button is pressed with no issues and then dies again a few minutes later. It does this repeatedly. So far we have done the following: Installed new fuel filter, all new fuel lines, a new fuel line to motor connecter, changed the oil and made sure its full. It doesnt seem like a fuel issue because it starts right back up? Any ideas?
 
Yes, run the engine until it cuts out, disconnect the temp sensor located between the spark plugs, see if it runs normally, but not for too long. If it fixes it, let me know and I will suggest next step
 
I will try as you advised. However, for clarification....after it dies, starts back up immediately and runs anywhere from a couple of minutes to 15 ish minutes. For me to know if this worked..... I would need to disconnect the temp sensor and run it for atleast 20 minutes without it dying to know if this worked. Tou mentioned not to run it for too long? Is 20 minutes too long?

Thank you for your response!
 
Splitting the fuel line is not a good installation. ---Each motor needs a separate fuel line from tank to motor.------Or valves needs to be installed.
 
Splitting the fuel line is not a good installation. ---Each motor needs a separate fuel line from tank to motor.------Or valves needs to be installed.

I mentioned this set up just in case this information resulted in someting to try. It was set up rhis way when he bought it new. Everything worked perfectly for approx 12 to 14 years so I didnt think it would be a contributing factor but wasnt sure. These issues just started over the last couple years.
 
Sorry,--missed the 12 to 14 year worked perfectly in post #1 I guess.----More trouble shooting is required.----Try running the 8 HP on a separate fuel tank.
 
Last edited:
Ian is probably right (usually is) about the temp sender putting the engine in protection shut down mode.
I just wanted to add that you DO need to be very cautious about how hot the engine gets when testing. So, your question about running it for 20 minutes with the sender unplugged is a good one. You can do that but you need to monitor for rising temperature while doing that. If you have an infrared temp gun this is pretty easy to do. The guns aren't terribly expensive and, if it keeps you from damaging the engine, it would be the best tool purchase you ever made.

If you don't want to buy one, the "good ol' boy" method of finding a spot that you can touch on the engine block (usually around the thermostat housing) while testing can give you some indication of temperature rise but with some accompanying pain to be sure. I've done it many times that way when I had nothing else and it works. There is, of course, the option of replacing the sensor with a mechanical temp gauge (my favorite for this) but it requires a bit of assembly to rig it up. For example the fitting needed to thread into the sender hole is something that you would probably need to order.

Putting your hand in the pee stream DOSEN'T work well because that is a bypass that takes the sample just as it enters the bottom of the engine and, thus, will be much cooler than the water cooling the block.

Question: has the thermostat ever been replaced? If it turns out that the sender isn't defective and the engine IS actually shutting down due to overheating the stat would be the next place to
check. It needs replacement every few seasons anyway. Also it should never be left permanently removed. Most people don't realize that the engine will actually overheat sooner in hard running without the thermostat than with it in place.

Like the others, I don't care much for the split fuel feed. Yes, it works and is "tidy" but a problem with it could actually disable both engines leaving you stranded. Just my opinion.

Hope you get it sorted out quickly.

Good luck.
 
Last edited:
Hi there, I finally got a chance to work on this today. Tried a seperate fuel line and it died in less than 4 minutes. Unplugged the temp sensor and ran it for 6 minute's and it didnt die! We are working on it right now. What shiuld we do next?
 
Inspect fuel pump and hose fittings.-----Clean the carburetor.----Check oil pressure switch if equipped with that item.
 
Inspect fuel pump and hose fittings.-----Clean the carburetor.----Check oil pressure switch if equipped with that item.

Before digging into to those things. Since disconnecting the heat sensor worked is there a way to tell if the heat sensor needs replaced or if its the thermostate or?
 
Your engne is over heating, most common causes, impeller, thermostat or clogged water gallery behind the exhaust plate- heavy salt build up around the internal anode is very common in saltwater usage. In extreme cases, if none of these fix the problem, then cylinder head galleries can also be blocked.
 
Your engne is over heating, most common causes, impeller, thermostat or clogged water gallery behind the exhaust plate- heavy salt build up around the internal anode is very common in saltwater usage. In extreme cases, if none of these fix the problem, then cylinder head galleries can also be blocked.

Thank you all for all the help. Replaced the impeller, temp sensor and thermostat. The impeller was in several pieces! It was still giving a good stream but I am guessing this was the issue. After these parts were replaced, everything seems to be working great now.

Thanks again
 
Back
Top